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<title>lwres_getaddrinfo</title>
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<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="refentry" lang="en">
<a name="id2476275"></a><div class="titlepage"></div>
<div class="refnamediv">
<h2>Name</h2>
<p>lwres_getaddrinfo, lwres_freeaddrinfo &#8212; socket address structure to host and service name</p>
</div>
<div class="refsynopsisdiv">
<h2>Synopsis</h2>
<div class="funcsynopsis">
<pre class="funcsynopsisinfo">#include &lt;lwres/netdb.h&gt;</pre>
<table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" style="padding-bottom: 1em">
<tr>
<td><code class="funcdef">
int
<b class="fsfunc">lwres_getaddrinfo</b>(</code></td>
<td>const char *�</td>
<td>
<var class="pdparam">hostname</var>, </td>
</tr>
<tr>
<td>�</td>
<td>const char *�</td>
<td>
<var class="pdparam">servname</var>, </td>
</tr>
<tr>
<td>�</td>
<td>const struct addrinfo *�</td>
<td>
<var class="pdparam">hints</var>, </td>
</tr>
<tr>
<td>�</td>
<td>struct addrinfo **�</td>
<td>
<var class="pdparam">res</var><code>)</code>;</td>
</tr>
</table>
<table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0"><tr>
<td><code class="funcdef">
void
<b class="fsfunc">lwres_freeaddrinfo</b>(</code></td>
<td>struct addrinfo *�</td>
<td>
<var class="pdparam">ai</var><code>)</code>;</td>
</tr></table>
</div>
<p>
      If the operating system does not provide a
      <span class="type">struct addrinfo</span>,
      the following structure is used:
    </p>
<pre class="programlisting">
struct  addrinfo {
        int             ai_flags;       /* AI_PASSIVE, AI_CANONNAME */
        int             ai_family;      /* PF_xxx */
        int             ai_socktype;    /* SOCK_xxx */
        int             ai_protocol;    /* 0 or IPPROTO_xxx for IPv4 and IPv6 */
        size_t          ai_addrlen;     /* length of ai_addr */
        char            *ai_canonname;  /* canonical name for hostname */
        struct sockaddr *ai_addr;       /* binary address */
        struct addrinfo *ai_next;       /* next structure in linked list */
};
</pre>
<p>
    </p>
</div>
<div class="refsect1" lang="en">
<a name="id2543412"></a><h2>DESCRIPTION</h2>
<p><code class="function">lwres_getaddrinfo()</code>
      is used to get a list of IP addresses and port numbers for host
      <em class="parameter"><code>hostname</code></em> and service
      <em class="parameter"><code>servname</code></em>.

      The function is the lightweight resolver's implementation of
      <code class="function">getaddrinfo()</code> as defined in RFC2133.
      <em class="parameter"><code>hostname</code></em> and
      <em class="parameter"><code>servname</code></em> are pointers to null-terminated
      strings or <span class="type">NULL</span>.

      <em class="parameter"><code>hostname</code></em> is either a host name or a
      numeric host address string: a dotted decimal IPv4 address or an
      IPv6 address.  <em class="parameter"><code>servname</code></em> is either a
      decimal port number or a service name as listed in
      <code class="filename">/etc/services</code>.
    </p>
<p><em class="parameter"><code>hints</code></em>
      is an optional pointer to a
      <span class="type">struct addrinfo</span>.
      This structure can be used to provide hints concerning the type of
      socket
      that the caller supports or wishes to use.
      The caller can supply the following structure elements in
      <em class="parameter"><code>*hints</code></em>:

      </p>
<div class="variablelist"><dl>
<dt><span class="term"><code class="constant">ai_family</code></span></dt>
<dd><p>
              The protocol family that should be used.
              When
              <code class="constant">ai_family</code>
              is set to
              <span class="type">PF_UNSPEC</span>,
              it means the caller will accept any protocol family supported by
              the
              operating system.
            </p></dd>
<dt><span class="term"><code class="constant">ai_socktype</code></span></dt>
<dd><p>
              denotes the type of socket &#8212;
              <span class="type">SOCK_STREAM</span>,
              <span class="type">SOCK_DGRAM</span>
              or
              <span class="type">SOCK_RAW</span>
              &#8212; that is wanted.
              When
              <code class="constant">ai_socktype</code>
              is zero the caller will accept any socket type.
            </p></dd>
<dt><span class="term"><code class="constant">ai_protocol</code></span></dt>
<dd><p>
              indicates which transport protocol is wanted: IPPROTO_UDP or
              IPPROTO_TCP.
              If
              <code class="constant">ai_protocol</code>
              is zero the caller will accept any protocol.
            </p></dd>
<dt><span class="term"><code class="constant">ai_flags</code></span></dt>
<dd>
<p>
              Flag bits.
              If the
              <span class="type">AI_CANONNAME</span>
              bit is set, a successful call to
              <code class="function">lwres_getaddrinfo()</code>
              will return a null-terminated string containing the canonical
              name
              of the specified hostname in
              <code class="constant">ai_canonname</code>
              of the first
              <span class="type">addrinfo</span>
              structure returned.
              Setting the
              <span class="type">AI_PASSIVE</span>
              bit indicates that the returned socket address structure is
              intended
              for used in a call to
              <span class="citerefentry"><span class="refentrytitle">bind</span>(2)</span>.

              In this case, if the hostname argument is a
              <span class="type">NULL</span>
              pointer, then the IP address portion of the socket
              address structure will be set to
              <span class="type">INADDR_ANY</span>
              for an IPv4 address or
              <span class="type">IN6ADDR_ANY_INIT</span>
              for an IPv6 address.
            </p>
<p>
              When
              <code class="constant">ai_flags</code>
              does not set the
              <span class="type">AI_PASSIVE</span>
              bit, the returned socket address structure will be ready
              for use in a call to
              <span class="citerefentry"><span class="refentrytitle">connect</span>(2)</span>
              for a connection-oriented protocol or
              <span class="citerefentry"><span class="refentrytitle">connect</span>(2)</span>,

              <span class="citerefentry"><span class="refentrytitle">sendto</span>(2)</span>,

              or
              <span class="citerefentry"><span class="refentrytitle">sendmsg</span>(2)</span>
              if a connectionless protocol was chosen.
              The IP address portion of the socket address structure will be
              set to the loopback address if
              <em class="parameter"><code>hostname</code></em>
              is a
              <span class="type">NULL</span>
              pointer and
              <span class="type">AI_PASSIVE</span>
              is not set in
              <code class="constant">ai_flags</code>.
            </p>
<p>
              If
              <code class="constant">ai_flags</code>
              is set to
              <span class="type">AI_NUMERICHOST</span>
              it indicates that
              <em class="parameter"><code>hostname</code></em>
              should be treated as a numeric string defining an IPv4 or IPv6
              address
              and no name resolution should be attempted.
            </p>
</dd>
</dl></div>
<p>
    </p>
<p>
      All other elements of the <span class="type">struct addrinfo</span> passed
      via <em class="parameter"><code>hints</code></em> must be zero.
    </p>
<p>
      A <em class="parameter"><code>hints</code></em> of <span class="type">NULL</span> is
      treated as if
      the caller provided a <span class="type">struct addrinfo</span> initialized to zero
      with <code class="constant">ai_family</code>set to
      <code class="constant">PF_UNSPEC</code>.
    </p>
<p>
      After a successful call to
      <code class="function">lwres_getaddrinfo()</code>,
      <em class="parameter"><code>*res</code></em>
      is a pointer to a linked list of one or more
      <span class="type">addrinfo</span>
      structures.
      Each
      <span class="type">struct addrinfo</span>
      in this list cn be processed by following
      the
      <code class="constant">ai_next</code>
      pointer, until a
      <span class="type">NULL</span>
      pointer is encountered.
      The three members
      <code class="constant">ai_family</code>,
      <code class="constant">ai_socktype</code>,
      and
      <code class="constant">ai_protocol</code>
      in each
      returned
      <span class="type">addrinfo</span>
      structure contain the corresponding arguments for a call to
      <span class="citerefentry"><span class="refentrytitle">socket</span>(2)</span>.
      For each
      <span class="type">addrinfo</span>
      structure in the list, the
      <code class="constant">ai_addr</code>
      member points to a filled-in socket address structure of length
      <code class="constant">ai_addrlen</code>.
    </p>
<p>
      All of the information returned by
      <code class="function">lwres_getaddrinfo()</code>
      is dynamically allocated: the addrinfo structures, and the socket
      address structures and canonical host name strings pointed to by the
      <code class="constant">addrinfo</code>structures.
      Memory allocated for the dynamically allocated structures created by
      a successful call to
      <code class="function">lwres_getaddrinfo()</code>
      is released by
      <code class="function">lwres_freeaddrinfo()</code>.
      <em class="parameter"><code>ai</code></em>
      is a pointer to a
      <span class="type">struct addrinfo</span>
      created by a call to
      <code class="function">lwres_getaddrinfo()</code>.
    </p>
</div>
<div class="refsect1" lang="en">
<a name="id2543789"></a><h2>RETURN VALUES</h2>
<p><code class="function">lwres_getaddrinfo()</code>
      returns zero on success or one of the error codes listed in
      <span class="citerefentry"><span class="refentrytitle">gai_strerror</span>(3)</span>
      if an error occurs.  If both <em class="parameter"><code>hostname</code></em> and
      <em class="parameter"><code>servname</code></em> are <span class="type">NULL</span>
      <code class="function">lwres_getaddrinfo()</code> returns
      <span class="errorcode">EAI_NONAME</span>.
    </p>
</div>
<div class="refsect1" lang="en">
<a name="id2543827"></a><h2>SEE ALSO</h2>
<p><span class="citerefentry"><span class="refentrytitle">lwres</span>(3)</span>,

      <span class="citerefentry"><span class="refentrytitle">lwres_getaddrinfo</span>(3)</span>,

      <span class="citerefentry"><span class="refentrytitle">lwres_freeaddrinfo</span>(3)</span>,

      <span class="citerefentry"><span class="refentrytitle">lwres_gai_strerror</span>(3)</span>,

      <span class="citerefentry"><span class="refentrytitle">RFC2133</span></span>,

      <span class="citerefentry"><span class="refentrytitle">getservbyname</span>(3)</span>,

      <span class="citerefentry"><span class="refentrytitle">bind</span>(2)</span>,

      <span class="citerefentry"><span class="refentrytitle">connect</span>(2)</span>,

      <span class="citerefentry"><span class="refentrytitle">sendto</span>(2)</span>,

      <span class="citerefentry"><span class="refentrytitle">sendmsg</span>(2)</span>,

      <span class="citerefentry"><span class="refentrytitle">socket</span>(2)</span>.
    </p>
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